Several of the new CCNA curriculum requirements have adapted the new features in Packet Tracer 6.1. Among these new features is the NetFlow network protocol analyzer. This feature allows us to collect data statistics and analyze the network traffic. This is very useful when then troubleshooting problems, or design issues. The data collected from various devices using UDP protocol is sent to NetFlow and is commonly called the (collector). The data collected in various formats form these devices are then displayed in the form of tables and charts for analysis. The NetFlow has many version, the latest being version 9.
What is Netflow?
NetFlow is a Cisco Propietary IOS application for collecting network IP traffic information. Simply said, Netflow provides detailed information on packets flowing through the network.
Now, Cisco defines a flow as a unidirectional sequence of packets with seven common values:
- Source IP address
- Destination IP address
- Source port number
- Destination port number
- Layer 3 protocol type
- Input logical interface
Enabling NetFlow technology on the network helps creates an environment in which you have the tools to understand how network traffic is flowing. Netflow can be likened to an itemized phone bill that shows all the numbers the user called, how frequently, time, duration etc.
Advantages of Netflow:
- Displays details of who uses network resources.
- Information can be used by business enterprises for accounting and charges for resource utilization.
- Detailed information can be used to do effective network planning.
- Information collected and analyzed can be used to customize network applications and services.
There are two tools used by Netflow for providing services on the network:
This is used for collecting data flow on the network.
This provides you with detailed, forensic-level information on top users on the network, data collected are usually preserved over time, you will be able to analyze network usage trends.
This tool enables you to analyze the traffic on your network by showing the users, protocols, and more. With netflow analyzer, you can view the types of traffic (web, mail, FTP, peer-to-peer, and so on) that are on the network; also which devices are using most of the traffic.
Netflow Network Components:
NetFlow components include the following:
- Network devices that are configured for NetFlow.
- NetFlow Collector, which receives NetFlow information from network devices
Netflow Network components or devices collect IP traffic information on interfaces where NetFlow is configured.
Network devices then export this information as NetFlow records to a central server that runs NetFlow Collector software, which also performs traffic analysis. Information captured and exported by NetFlow is done independently on each internetworking device or component. NetFlow does not need to be configured on each router in the network.
In this lab we will use Cisco’s Packet Tracer to configure a small network consisting of few different devices. We will use this topology to demonstrate how to configure to configure NetFlow version 9 on a Cisco IOS.
Configuring the protocol is relatively simple. First it is necessary to insure the Cisco Express Forwarding (CEF) is enabled, this is the default on most new cisco devices, but you should check if it is on the device you are using.
Router # show ip cef
To enable Cisco Express Forwarding (CEF) do the following:
Router # config t
Router (config) # ip cef
Then the interface selected must be configured to monitor traffic. There are two methods; however only one of them is supported in Packet Tracer. For example, if you want all incoming (ingress) and outbound (egress) traffic to be collected on the Fa0 / 0 interface, you would enter the following commands:
Router # config t
Router (config) # interface Fa0 / 0
Router (config-if) # ip flow ingress
Router (config-if) # ip flow egress
Then configure the device so the data can be sent to the collector:
Router # config t
Router (config) # ip flow-export source Fa0 / 0
Router (config) # ip flow-export destination 192.168.100.100 9996
Router (config) # ip flow-export version 9
The Traffic can now be displayed on the selected computer using the NetFlow appliclation.
NetFlow (161.1 KiB, 2,898 hits)
Packet Tracer 6.2 (54.9 MiB, 1,194 hits)
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